1. Field of the Invention
The present invention relates generally to near field communications.
2. Background Art
Near field communication, or NFC, is a set of short-range wireless technologies, typically requiring a distance of 4 cm or less. NFC generally operates at 13.56 MHz and at rates ranging from about 106 kbit/s to 848 kbit/s. NFC generally involves a reader (or initiator) and a tag (or target); the reader actively generates an RF field that can power a passive tag. This enables NFC tags to be configured so as to have very simple form factors such as tags, stickers, key fobs, or cards that do not require batteries. NFC peer-to-peer communication is of course possible, where both devices are powered. Devices that contain both reader and tag capabilities are often called controllers.
Near field communications (NFC) devices can be integrated into mobile devices, such as smartphones, for example, to facilitate the use of these mobile devices in conducting daily transactions. For example, instead of carrying numerous credit cards, the credit information provided by these credit cards could be stored onto a NFC device. The NFC device is simply tapped to a credit card terminal to relay the credit information to it to complete a transaction. As another example, ticket writing systems, such as those used in bus and train terminals, may simply write ticket fare information onto the NFC device instead of providing a paper ticket to a passenger. The passenger simply taps the NFC device to a reader to ride the bus or the train without the use of a paper ticket.
Generally, NFC requires that NFC devices be present within a relatively close proximity to each other so that their corresponding magnetic fields can exchange information. Typically, a first NFC device transmits or generates a magnetic field modulated with the information, such as the credit information or the ticket fare information. This magnetic field inductively couples onto a second NFC device that is proximate to the first NFC device. The second NFC device may respond to the first NFC device by transmitting or generating its own modulated magnetic field and inductively coupling this magnetic field to the first NFC device.
Mobile communication devices, such as smartphones, tablet computers, notebook computers, and the like, are generally battery powered. The battery in these devices has a finite life before it requires recharging. Manufacturers of mobile devices that incorporate NFC devices generally want them to be able to operate as card emulators. In card emulation mode, the mobile device can take the place of a credit or debit card to make purchases or perform other financial tasks that cards can normally accomplish. In addition, in card emulation mode, the mobile device may be used to access transportation systems, allowing a user to enter and/or exit a subway or bus system, for example. It is desirable to incorporate features into the mobile communication devices that will allow them to operate in card emulation mode even when they cannot be used to make or receive calls or access the Internet.
The present invention will be described with reference to the accompanying drawings. Generally, the drawing in which an element first appears is typically indicated by the leftmost digit(s) in the corresponding reference number.